I have a spare 942 4 bolt short block with a casting date of Sept 21, 1965 (no #'s on the pad). Is there consensus in the hobby as to when the early 66 427 cars switched from 450 to 425? Are there distinguishing internal or external features that differentiate the two? Noland Adams book indicates on pg 345 that VIN 103545 (3rd week Oct assembly) was a 450. A Sept 28th 1965 ordered car - ordered as a 450 VIN 108947 was delivered in Dec 65 as a 425. Is Sept 21 65 cast 4 bolt a 450hp and if so - is it more sought after then a later 425hp ?
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Re: 450hp or 425hp ?
The Restorer ran an artical on this a couple issues back I believe. I seem to remember the engines were identical except for the decal on the air cleaner.
Also seem to remember some original owners even got the 450 hp decal in their owners packet. Pesky regulations of some kind prevented GM from providing the decal attached to the car.
The feds are our friends though...don't ever forget it.
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Re: 450hp or 425hp ?
Peter-----
There are absolutely no functional differences between a "425" hp and a "450" hp 427. The difference lies ONLY in the horsepower label affixed to the air cleaner perimeter. That's it. Given the fact that there were no other differences, that's why it's so difficult to document the "changeover". Labels on air cleaners are quite easy to change.In Appreciation of John HinckleyComment
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Re: 450hp or 425hp ?
the insurance companies were on these high HP cars back then. when i tried to sell my 450 HP corvette in the fall of 66 anyone that wanted to buy it had the problem of the monthly insurance payment being more than the car payment. i did not sell the car till the fall of 67 so i did not get my new Z-28 till the 68 model. i needed more seats because my son came along in 66Comment
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Re: 450hp or 425hp ?
As the post-66 team leader, i don't think a 450 hp decal ever got affixed to a 66 425 hp air cleaner. mikeComment
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Re: 450hp or 425hp ?
I know zero about the specifics relative to 450 versus 425 HP. I do know this is about the time the General was wrangling with horsepower versus weight, factor limits, etc. I do not recall the pounds per HP specifics, but my thought would be it was a GM/Chevrolet mandate, not a fed thing. Might the Raucous Silence book be a possible source for some info along these lines?
Roger
#36316Comment
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Many engine specs were an outright lie...
You'd think the numbers were inflated to impress potential buyers, but actually the top performing engines were almost universally under-rated to make paying for the insurance possible. One of the most flagrant examples I know the actual numbers for was the BOSS 302. When the cars were still in the showroom, the parts department had books for sale on how to build up the plain small-head 302 2V to over 350hp. The BOSS was basically an SCCA race-ready engine, barely driveable on the street, and yet all the brochures spec it at 290hp. I'm told dyno testing puts a more accurate claim near 400hp. At the time, of course, everyone (except insurance companies) knew this about supercar engines ;-)Comment
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Your Block...
As stated there were no differences between 450 and 425 HP engines - paperwork was the only difference. However, early 427 blocks (942 and 961) are of interest for another reason - some early castings have the reinforcing ribs like the 396 block. My two blocks dated Sept 20 and 21 do not have the ribs but there is reportedly a block dated Sept 22 with ribs. I am surveying early 427 blocks and would like to know if yours has the ribs (there are two vertical ribs on the front of the block between the timing cover and the intake, and there are two on the rear of the block). Note that the presence of ribs does NOT make a 450 block. Most cars with 450 paper do not have ribs on the blocks.Comment
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Re: 450hp or 425hp ?
Is this 942 spare block for sale?Comment
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Re: 450hp or 425hp ?
Used original blocks can be found on eBay, from various folks advertizing in the NCRS Driveline magazine, in Hemmings Motor News, sometimes locally at this/that machine shop; so it's a matter of shopping/looking. The day of finding a ready-to-drop-in crate motor is pretty much a dead horse....Comment
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